Dissolved Oxygen Test Results

[Beverly]

Sam,

Interesting results. I am wondering if you had windows open at some point during the day that got closed partially or fully at night. With open windows, you will be getting a constant supply of O2 from outside that will get introduced into your tank by your PHs, airstones, AC 200. With closed or partially closed windows, the amount of O2 in the room available to go into your tank would be decreased.

Can you address the open/closed windows issue with regard to your experiment?

I have a 28g bowfront with 85w PC lighting and two Hagen 301 powerheads. I notice a significant amount of air bubbles on the macroalgae in that tank starting about midway through the day. MA in that tank is growing to beat the band. Windows are open all day and night now that it's spring. Don't have a DO meter to measure what's actually going on in the tank, though.